THE year was 1916. Australian soldiers involved in the brutal fighting on the Western Front had been granted leave and went to Ireland for a break.

But instead of catching up with relatives and resting up, the Australian troops found themselves reluctantly pressed into more action by the British — to help crush the Easter Rebellion in Dublin.

Some of the Anzacs involved in this little-known episode were Gallipoli veterans prized by the British for their sharp-shooting skills.

One group was ordered onto the roof of Dublin's Trinity College to snipe at Irish dispatch riders delivering messages to the the headquarters of the rebels, whose leaders included Michael Collins.

Barrister and historian Jeff Kildea has researched the episode and described the colonial soldiers' dilemma in a new book, Anzacs and Ireland..

"For soldiers who enlisted to fight Germans, it was not a happy time," Mr Kildea said.

These veterans of Gallipoli went to Ireland on leave but found themselves once again in battle, he said. "(They were) given a rifle and, in effect, told to shoot their Irish 'cousins'."

...when the fighting erupted in Dublin, many of the soldiers on leave were rounded up by British officers in hotels and clubs and at the local railway station and had rifles thrust back into their hands.

Mr Kildea found the diary of Private Davis, who described how the soldiers made the best of a bad job — "but we would prefer to be anywhere but this unenviable city".

Davis and a friend were ordered to join 70 men taking arms and ammunition to Dublin Castle and described how a volley of rifle shots rained down on the party from buildings the rebels occupied. "Around us bullets pinged and broken glass clattered onto the footpath.

"The horses bolted and vanished into the darkness and the troops did likewise."

The British military aristocracy of the World War I era saw little difference between Australian diggers and Irish revolutionaries. They were all just human pawns for them to pit against their enemies, or in this case, each other.

No doubt amongst the Diggers in Ireland there were those who refused to kill their Irish 'cousins' and those who were threatened with a bullet to the head from British sergeants for refusing to obey orders.

Those who ran away didn't necessarily do so simply because they were scared.